Deep bed filtration : mathematical models and observations

Numerous mathematical models have been developed to evaluate both initial and transient stage removal efficiency of deep bed filters. Microscopic models either using trajectory analysis or convective diffusion equations were used to compute the initial removal efficiency. These models predicted the removal efficiency under favorable filtration conditions quantitatively, but failed to predict the removal efficiency under unfavorable conditions. They underestimated the removal efficiency under unfavorable conditions. Thus, semi-empirical formulations were developed to compute initial removal efficiencies under unfavorable conditions. Also, correction for the adhesion of particles onto filter grains improved the results obtained for removal efficiency from the trajectory analysis. Macroscopic models were used to predict the transient stage removal efficiency of deep bed filters. The O’Melia and Ali1 model assumed that the particle removal is due to filter grains as well as the particles that are already deposited onto the filter grain. Thus, semi-empirical models were used to predict the ripening of filtration. Several modifications were made to the model developed by O’Melia and Ali to predict the deterioration of particle removal during the transient stages of filtration. Models considering the removal of particles under favorable conditions and the accumulation of charges on the filter grains during the transient stages were also developed. This article evaluates those models and their applicability under different operating conditions of filtration.

Quantities of foods consumed by 12- to 24-month-old New Zealand children

Aim:  The present study aimed to estimate small, median and large daily quantities of frequently consumed foods and identify which food groups are important sources of key micronutrients for 12- to 24-month-old New Zealand children.

Methods:  A community-based cross-sectional survey was conducted in three cities in the South Island of New Zealand. Healthy toddlers (n = 188) were randomly selected using multistage sampling. Three non-consecutive 1-day weighed food records were collected from each child and the frequencies and daily quantities of foods and beverages, and important sources of iron and zinc, were determined.

Results:  Fifty percent or more of the children consumed the following foods at least once over 3 days (median gram intake among toddlers who consumed the food): milk (366 g), white bread (29 g), banana (70 g), potato (34 g), cheese (12 g), apple (39 g), ‘Weetbix’ whole-wheat breakfast cereal (16 g), yeast extract spread (‘Marmite’, ‘Vegemite’) (2 g), carrot (17 g) and margarine (4 g). Dairy, cereals and the meat/fish/poultry/eggs/nuts food group were the most important sources of iron and zinc in the toddlers' diets, providing 69.1% of iron and 86.3% of zinc.

Conclusion:  This research provides dietitians, other health professionals, researchers and policy-makers with detailed information on daily quantities of foods and beverages frequently consumed by toddlers that can be used for dietetic counselling, dietary assessment, and to develop food-based dietary guidelines specifically for toddlers.

Behavior and weight correlates of weight-control efforts in Australian women living in disadvantage : the READI study

Background
With increasing obesity rates worldwide, more and more people are actively attempting to lose weight or avoid weight gain, but relatively little is known about what specific behaviors comprise these efforts and which, if any, are associated with better weight control over time.

Methods
This paper reports relationships between body weight, weight-control efforts and related behaviors over a three-year period in 1,634 Australian women. The women were purposefully recruited from 80 disadvantaged neighborhoods in Victoria, Australia. Weight loss efforts were categorized as trying to lose weight, trying to prevent weight gain and no weight-control efforts. Behavioral correlates examined included different kinds of physical activity and consumption of a number of specific foods types.

Results and discussion
Self-reported body weight at baseline was higher in women trying to lose weight. Frequency of consumption of low energy density foods was positively associated with reported weight-control efforts, as was frequency of reported total and leisure-time physical activity. Longitudinal associations between changes in weight-control efforts and changes in behaviors were consistent with the cross-sectional findings. At three-year follow up, however, weight-control efforts were not associated with change in body weight. More detailed analyses of specific food choices suggested that part of the explanation of no effect of reported weight-control efforts and weight over time might be that people are not as well-informed as they should be about the energy density of some common foods. In particular, those reporting engagement in weight-control efforts reported reducing consumption of carbohydrate-containing foods such as bread and potatoes more than is justified by their energy content, while they reported increasing consumption of some high energy density foods (e.g., cheese and nuts).

Conclusion
It is tentatively concluded that women living in disadvantaged neighborhoods understand messages about weight-control (more activity and foods with lower fat and lower energy density) but that some foods eaten more by women engaged in weight control may reduce the effectiveness of these efforts.

Maternal hair selenium levels as a possible long-term nutritional indicator of recurrent pregnancy loss

BackgroundApproximately 1% of all couples trying to conceive will suffer from recurrent pregnancy loss (RPL). Nutritional deficiencies have been postulated as a possible cause of RPL and in particular, selenium deficiency has been associated with reproductive failure in animal studies and more recently, in some human studies. This study was undertaken to assess the maternal hair selenium levels in women with RPL without an identified cause and to compare these results with those of women with successful reproductive histories.MethodsTwenty four patients with RPL and twenty four control subjects with at least one successful pregnancy and no pregnancy failures, who were matched for age and ethnicity, were recruited. A questionnaire was completed, which included demographic and social information and a dietary history. Hair samples were collected and analyzed for selenium content by inductively coupled plasma mass spectrometry.ResultsThe control subjects had a higher mean income and had completed more years of education compared with the RPL patients. There was no significant difference in the intake of selenium rich foods between the 2 groups. The patients, however, consumed significantly more fruit, cheese, potatoes and chocolate than the controls. The median (range) selenium content was 0.80 ppm (0.19-4.15) and 0.68 ppm (0.43-3.76) in patients and controls respectively (Mann Whitney U test 209.5 p = 0.74).ConclusionsWhile there were significant differences in the 2 groups with regard to resources, education and diet our results show that hair selenium concentrations and dietary selenium intake, were similar in the two groups. Both groups had low levels of this important element.

Designing a healthy food partnership: lessons from the Australian food and health dialogue

BACKGROUND: Poor diets are a leading cause of disease burden worldwide. In Australia, the Federal Government established the Food and Health Dialogue (the Dialogue) in 2009 to address this issue, primarily through food reformulation. We evaluated the Dialogue's performance over its 6 years of operation and used these findings to develop recommendations for the success of the new Healthy Food Partnership.

METHODS: We used information from the Dialogue website, media releases, communiqués, e-newsletters, materials released under freedom-of-information, and Parliamentary Hansard to evaluate the Dialogue's achievements from October 2013 to November 2015, using the RE-AIM (reach, efficacy, adoption, implementation and maintenance) framework. We also engaged closely with two former Dialogue members. Our findings update a prior assessment done in October 2013.

RESULTS: Little data is available to evaluate the Dialogue's recent achievements, with no information about progress against milestones released since October 2013. In the last 2 years, only one additional set of sodium reduction targets (cheese) was agreed and Quick Service Restaurant foods were added as an area for action. Some activity was identified in 12 of a possible 137 (9 %) areas of action within the Dialogue's mandate. Independent evaluation found targets were partially achieved in some food categories, with substantial variation in success between companies. No effects on the knowledge, behaviours or nutrient intake of the Australian population or evidence of impact on diet-related disease could be identified.

CONCLUSIONS: The new Healthy Food Partnership has similar goals to the Dialogue. While highly laudable and recognised globally as cost-effective, the mechanism for delivery in Australia has been woefully inadequate. Strong government leadership, adequate funding, clear targets and timelines, management of conflict of interest, comprehensive monitoring and evaluation, and a plan for responsive regulation in the event of missed milestones will be required if the new Healthy Food Partnership is to achieve its urgent public health goals.